This invention relates to a novel catalytic reactor and method for loading thereof. Apparatuses for catalytic treatment, for example, desulfurization, of distillate fractions are known. In operation, such an apparatus generally contains 10-100 m.sup.3 of catalyst distributed over one or more beds which have to be purified after a period of time, not so much on account of a decline in catalyst activity, but rather as a consequence of contamination ultimately resulting in an excessive pressure drop across the catalyst bed. For the purpose of this purification, it is frequently necessary for the contaminated catalyst to be removed from the apparatus, requiring entry by personnel into the opened reactor in order to remove consecutively the supporting means of the beds situated one above the other. Since any iron sulphide formed during desulphurization is often pyrophoric, it is desirable that the catalyst should first be deactivated in this respect. After dismantling, the reactor beds have to be built up again by reassembling the supporting means and loading with fresh or purified catalyst. The rate at which catalyst can be unloaded from such a reactor is approximately 4 m.sup.3 /hr, and the loading rate is approx. 6 m.sup.3 /hr. Since this unloading of the catalyst is necessary at most once a year, the loss of time involved in the shut-down and renewal of the bed does not form an insuperable drawback in the case of this size of apparatus. It is a more serious matter, however, in the case of larger apparatuses designed for the desulphurization of petroleum residues. To operate efficiently and economically, such an apparatus often has a much larger catalyst charge of the order of 500-1000 m.sup.3. In residue desulphurization, the bed not only becomes contaminated but moreover the catalyst activity declines relatively rapidly not so much because of coke formation as a result of the presence of asphaltenes, but rather by deposition, in the pores of the catalyst, of metals present in the petroleum residue. This may contribute towards necessitating much more frequent loading with fresh catalyst, for example once every six months. At the above-mentioned average catalyst handling rate of 5 m.sup.3 /hr., 10 to 20 days are required for the unloading of the catalyst and the loading of the fresh catalyst. This means an annual loss of 10% or more of the operating time on account of this catalyst replacement. If an effort is made to compensate for this loss of time by increasing the capacity of the reactor, considerable additional capital expenditure is required.